@article{davies_evidence_2019,
	title = {Evidence for {Low} {Radiative} {Efficiency} or {Highly} {Obscured} {Growth} of \$z{\textgreater}7\$ {Quasars}},
	volume = {1906},
	url = {http://adsabs.harvard.edu/abs/2019arXiv190610130D},
	abstract = {The supermassive black holes (SMBHs) observed at the centers of all 
massive galaxies are believed to have grown via luminous accretion
during quasar phases in the distant past. The fraction of inflowing rest
mass energy emitted as light, the radiative efficiency, has been
inferred to be 10{\textbackslash}\%, in agreement with expectations from thin disk
accretion models. But the existence of billion solar-mass SMBHs powering
quasars at \$z {\textgreater} 7\$ challenges this picture: provided they respect the
Eddington limit, there is not enough time to grow \$z{\textgreater}7\$ SMBHs from
stellar remnant seeds unless the radiative efficiency is below 10{\textbackslash}\%.
Here we show that one can constrain the radiative efficiencies of the
most distant quasars known using foreground neutral intergalactic gas as
a cosmological-scale ionizing photon counter. From the Ly\${\textbackslash}alpha\$
absorption profiles of ULAS J1120+0641 (\$z=7.09\$) and ULAS J1342+0928
(\$z=7.54\$), we determine posterior median radiative efficiencies of
0.08{\textbackslash}\% and 0.1{\textbackslash}\%, respectively, and the combination of the two
measurements rule out the canonical 10{\textbackslash}\% efficiency at 99.8{\textbackslash}\%
credibility after marginalizing over the unknown obscured fraction. This
low radiative efficiency implies rapid mass accretion for the earliest
SMBHs, greatly easing the tension between the age of the Universe and
the SMBH masses. However, our measured efficiency may instead reflect
nearly complete obscuration by dusty gas in the quasar host galaxies
over the vast majority of their SMBH growth. Assuming 10{\textbackslash}\% efficiency
during unobscured phases, we find that the obscured fraction would be
\${\textgreater}82{\textbackslash}\%\$ at 95{\textbackslash}\% credibility, and imply a \$25.7{\textasciicircum}\{+49.6\}\_\{-16.5\}\$ times
larger obscured than unobscured luminous quasar population at \$z{\textgreater}7\$.},
	urldate = {2019-07-01},
	journal = {arXiv e-prints},
	author = {Davies, Frederick B. and Hennawi, Joseph F. and Eilers, Anna-Christina},
	month = jun,
	year = {2019},
	keywords = {Astrophysics - Astrophysics of Galaxies},
	pages = {arXiv:1906.10130},
}

{"_id":"HTzsSq8HLDsFnsrsX","bibbaseid":"davies-hennawi-eilers-evidenceforlowradiativeefficiencyorhighlyobscuredgrowthofztextgreater7quasars-2019","author_short":["Davies, F. B.","Hennawi, J. F.","Eilers, A."],"bibdata":{"bibtype":"article","type":"article","title":"Evidence for Low Radiative Efficiency or Highly Obscured Growth of \\$z{\\textgreater}7\\$ Quasars","volume":"1906","url":"http://adsabs.harvard.edu/abs/2019arXiv190610130D","abstract":"The supermassive black holes (SMBHs) observed at the centers of all massive galaxies are believed to have grown via luminous accretion during quasar phases in the distant past. The fraction of inflowing rest mass energy emitted as light, the radiative efficiency, has been inferred to be 10\\textbackslash%, in agreement with expectations from thin disk accretion models. But the existence of billion solar-mass SMBHs powering quasars at \\$z {\\textgreater} 7\\$ challenges this picture: provided they respect the Eddington limit, there is not enough time to grow \\$z{\\textgreater}7\\$ SMBHs from stellar remnant seeds unless the radiative efficiency is below 10\\textbackslash%. Here we show that one can constrain the radiative efficiencies of the most distant quasars known using foreground neutral intergalactic gas as a cosmological-scale ionizing photon counter. From the Ly\\${\\textbackslash}alpha\\$ absorption profiles of ULAS J1120+0641 (\\$z=7.09\\$) and ULAS J1342+0928 (\\$z=7.54\\$), we determine posterior median radiative efficiencies of 0.08\\textbackslash% and 0.1\\textbackslash%, respectively, and the combination of the two measurements rule out the canonical 10\\textbackslash% efficiency at 99.8\\textbackslash% credibility after marginalizing over the unknown obscured fraction. This low radiative efficiency implies rapid mass accretion for the earliest SMBHs, greatly easing the tension between the age of the Universe and the SMBH masses. However, our measured efficiency may instead reflect nearly complete obscuration by dusty gas in the quasar host galaxies over the vast majority of their SMBH growth. Assuming 10\\textbackslash% efficiency during unobscured phases, we find that the obscured fraction would be \\${\\textgreater}82{\\textbackslash}%\\$ at 95\\textbackslash% credibility, and imply a \\$25.7{\\textasciicircum}\\{+49.6\\}_\\{-16.5\\}\\$ times larger obscured than unobscured luminous quasar population at \\$z{\\textgreater}7\\$.","urldate":"2019-07-01","journal":"arXiv e-prints","author":[{"propositions":[],"lastnames":["Davies"],"firstnames":["Frederick","B."],"suffixes":[]},{"propositions":[],"lastnames":["Hennawi"],"firstnames":["Joseph","F."],"suffixes":[]},{"propositions":[],"lastnames":["Eilers"],"firstnames":["Anna-Christina"],"suffixes":[]}],"month":"June","year":"2019","keywords":"Astrophysics - Astrophysics of Galaxies","pages":"arXiv:1906.10130","bibtex":"@article{davies_evidence_2019,\n\ttitle = {Evidence for {Low} {Radiative} {Efficiency} or {Highly} {Obscured} {Growth} of \\$z{\\textgreater}7\\$ {Quasars}},\n\tvolume = {1906},\n\turl = {http://adsabs.harvard.edu/abs/2019arXiv190610130D},\n\tabstract = {The supermassive black holes (SMBHs) observed at the centers of all \nmassive galaxies are believed to have grown via luminous accretion\nduring quasar phases in the distant past. The fraction of inflowing rest\nmass energy emitted as light, the radiative efficiency, has been\ninferred to be 10{\\textbackslash}\\%, in agreement with expectations from thin disk\naccretion models. But the existence of billion solar-mass SMBHs powering\nquasars at \\$z {\\textgreater} 7\\$ challenges this picture: provided they respect the\nEddington limit, there is not enough time to grow \\$z{\\textgreater}7\\$ SMBHs from\nstellar remnant seeds unless the radiative efficiency is below 10{\\textbackslash}\\%.\nHere we show that one can constrain the radiative efficiencies of the\nmost distant quasars known using foreground neutral intergalactic gas as\na cosmological-scale ionizing photon counter. From the Ly\\${\\textbackslash}alpha\\$\nabsorption profiles of ULAS J1120+0641 (\\$z=7.09\\$) and ULAS J1342+0928\n(\\$z=7.54\\$), we determine posterior median radiative efficiencies of\n0.08{\\textbackslash}\\% and 0.1{\\textbackslash}\\%, respectively, and the combination of the two\nmeasurements rule out the canonical 10{\\textbackslash}\\% efficiency at 99.8{\\textbackslash}\\%\ncredibility after marginalizing over the unknown obscured fraction. This\nlow radiative efficiency implies rapid mass accretion for the earliest\nSMBHs, greatly easing the tension between the age of the Universe and\nthe SMBH masses. However, our measured efficiency may instead reflect\nnearly complete obscuration by dusty gas in the quasar host galaxies\nover the vast majority of their SMBH growth. Assuming 10{\\textbackslash}\\% efficiency\nduring unobscured phases, we find that the obscured fraction would be\n\\${\\textgreater}82{\\textbackslash}\\%\\$ at 95{\\textbackslash}\\% credibility, and imply a \\$25.7{\\textasciicircum}\\{+49.6\\}\\_\\{-16.5\\}\\$ times\nlarger obscured than unobscured luminous quasar population at \\$z{\\textgreater}7\\$.},\n\turldate = {2019-07-01},\n\tjournal = {arXiv e-prints},\n\tauthor = {Davies, Frederick B. and Hennawi, Joseph F. and Eilers, Anna-Christina},\n\tmonth = jun,\n\tyear = {2019},\n\tkeywords = {Astrophysics - Astrophysics of Galaxies},\n\tpages = {arXiv:1906.10130},\n}\n\n","author_short":["Davies, F. B.","Hennawi, J. F.","Eilers, A."],"key":"davies_evidence_2019","id":"davies_evidence_2019","bibbaseid":"davies-hennawi-eilers-evidenceforlowradiativeefficiencyorhighlyobscuredgrowthofztextgreater7quasars-2019","role":"author","urls":{"Paper":"http://adsabs.harvard.edu/abs/2019arXiv190610130D"},"keyword":["Astrophysics - Astrophysics of Galaxies"],"metadata":{"authorlinks":{}}},"bibtype":"article","biburl":"https://bibbase.org/zotero/polyphant","dataSources":["7gvjSdWrEu7z5vjjj"],"keywords":["astrophysics - astrophysics of galaxies"],"search_terms":["evidence","low","radiative","efficiency","highly","obscured","growth","textgreater","quasars","davies","hennawi","eilers"],"title":"Evidence for Low Radiative Efficiency or Highly Obscured Growth of \\$z{\\textgreater}7\\$ Quasars","year":2019}